Membrane, a method and die means for manufacturing same

ABSTRACT

The invention relates to a method of manufacturing a membrane ( 1 ) from a blank ( 39 ) by a cure, which membrane comprises two rubber layers ( 40, 41 ) and a fabric-formed reinforcement layer ( 19 ), positioned between said rubber layers. In order to counteract and prevent respectively undesirable displacements of the reinforcement layer ( 19 ) membrane sections, which are movable in an application position, are manufactured according to the invention having a form, which deviates from the application form, and/or are exposed to stretching during the cure in order to within the membrane section bring about a displacement of said reinforcement layer ( 19 ) across a portion of at least one of the rubber layers ( 40, 41 ) and consequently a position, which deviates from the blank building up during the cure. The invention also relates to a membrane, manufactured according to this method as well as a mold tool designed to carry out the method and the manufacture of the membrane respectively.

The present invention relates to a method of manufacturing a membraneaccording to the preamble of claim 1. Also, the invention relates to amembrane according to the preamble of the first means claim as well as amold tool, designed to carry out said method and to manufacture saidmembrane respectively.

According to already known technology, when base materials forreinforced membranes are manufactured, one or several reinforcementlayers, made of e.g. fabrics, are placed between two or several layersof a rubber elastic material, particularly rubber, and the layers arejoined, e.g. through calendering. Alternatively the various layers canbe placed on top of each other in a mold tool for membranemanufacturing. In the two cases these layers are permanently joined toeach other by a cure process.

During the cure the rubber turns semi-liquid and penetrates into thereinforcement material layer and the various rubber layers, if severalare used, are joined to each other through e.g. quite thin fabrics. Thereinforcement layer will then at least mainly retain its position.However, when membranes are cured in this way, the final shaping of themembranes takes place at the same time. During more accentuated shapingof this type, with e.g, sharp bends with small radius, varyingstretching and press forces are exerted on the reinforcement as well asthe semi-liquid rubber layers. Then the semi-liquid rubber in one layermay be pushed aside in a planar direction and/or across thereinforcement layer and into another rubber layer, particularly when thereinforcement layer consists of a thin fabric. The reinforcement layerthen moves in an undesirable way and occupies in the finished membraneanother position than the desired one. Such an undesirable displacementof the reinforcement layer may in a typical case result in, that thereinforcement will be located close to a pressurized liquid or gas,which penetrates the reinforcement layer and expands the rubber layer onthe other side to a bubble. Also, quite generally reinforcementdisplacements in relation to the desired position results in risks offunctional disturbances, e.g. due to changes in the desired movabilityof the membrane and its elastic deformation performance, as well asrisks of quality impairment.

The object of the present invention is to prevent and as far as possibleeliminate the above-mentioned drawbacks as well as in other respectsdevelop the state of the art in this technical field and find newapplication possibilities. In all cases undesirable displacements of thereinforcement layer or layers will be counteracted or prevented, eithera desired displacement of the reinforcement layer or layers taking placewithin the blank or the blanks or no such displacement taking placeand/or a desired stretching or prestressing of the reinforcement layeror layers being obtained, the results depending on the membrane designand the application respectively.

This object is attained according to the invention through a method ofthe type described in the introduction, which method is set forth in thecharacterizing clause of claim 1. Said object is also attained by meansof a membrane, which is designed mainly according to the characterizingclause of the first means claim, and by means of a form tool accordingto the first form tool claim respectively. Additional characterizingfeatures and advantages of the present invention are set forth in thefollowing description, reference being made to the accompanyingdrawings, which depict a few preferred but not limiting embodiments ofthe invention. The drawings show in detail in diametrical, partlyschematic cross sections in:

FIG. 1 the manufacturing position and the application position of aconventional membrane;

FIG. 2 the manufacturing position of a membrane according to theinvention;

FIG. 3 the application position of the membrane according to FIG. 2;

FIGS. 4 and 5 a modified manufacturing position and an applicationposition of another membrane according to the invention;

FIGS. 6 and 7 ditto for a third membrane according to the invention;

FIGS. 8 and 9 ditto for a fourth membrane according to the invention;

FIGS. 10-12 successive steps of the manufacturing according to theinvention of a membrane according to FIGS. 4-9, when a form toolaccording to the invention is used.

A membrane 1 according to FIG. 1 preferably is manufactured jointly withand possibly is simultaneously cured on a support plate 2, e.g. made ofa metal, in the shown membrane shape or form, which also is theapplication form. The support place has e.g. a ring portion 3 with anupper bearing surface 4, which has a radial extension, and with aconnected, outer, somewhat longer axial flange 5 all around as well as aalso connected inner, somewhat shorter axial wall 6 all around, the edgeof which, which faces the bearing surface, being connected to a bottom7, disposed in a radial plane and having a central circular hole 8.Between flange 5 and wall 6 spokes 9 may extend.

Membrane 1 is applied around hole 8 to come in contact with the lowerside of bottom 7 against an edge area around hole 8. The membrane thenfollows the hole wall and the upper side of the bottom, wall 6 as wellas bearing surface 4, which extends outwards in the form of a shortprojection 10 of the ring portion having an upper bend 11 and a lower,more accentuated or sharp step 12, which is a practical necessity inorder to be able to connect a mold tool part to the support plate. Themembrane follows the bend and axial outer side 13 of the projection andthen continues in the form of a sweeping, from said step extending, inits cross section roughly circular arc-shaped curve 14 downwards andthen upwards, and then continues in the form of an axial straight part15 rearwards in relation to the initial phase of the described curveinto a level above or axially in front of the bearing surface in orderto in that location be terminated in the form of a bead 16,substantially circular in its cross section and which mainly can bedisposed inside the area enclosed by said straight part and an imaginarycontinuation of same respectively.

The design now described is of course rotation symmetrical and thepurpose is to let bead 16 be sealingly clamped up between e.g. twostationary valve parts (not shown), whereas hole 8 and the adjoiningmembrane portion will be applied on e.g. a valve spindle (not shown),and adjacent the bottom special bearing or fastening means (not shown)can be provided. The membrane for the rest is, jointly with an optionalsupport plate, axially movably mounted, the movements mainly beingdesigned to, during elastic deformation, be absorbed by curve 14 and theadjoining membrane portions. In the typical case, which is shown in FIG.1, at least periodically there can be a higher pressure in a liquid or agas on the upper or outer fastening side 17 of the membrane, where thusthe concave portion of curve 14 mainly is exposed to the pressure drop.Side 17 is the pressure side, when the membrane is used or applied aswell as when it is manufactured, in the latter case because a mold part,designed as an upper-die is used to create the curve and a certaintension in the plane starting layer of the membrane blank around theupper-die portions cannot be avoided.

It is shown in the enlarged portion of FIG. 1, that during the curesoftened rubber layer 18 of the membrane is removed from the concaveside of the curve and through reinforcement layer 19 of the membrane andto the concave side, the reinforcement material almost ending up on thesurfaced within the inner side of the curve. This may result in, thatpressurized liquids or gases, which influence the inner side of thecurve, in an almost uncontrollable way will act through thereinforcement material and against the rubber layer on the other side ofthe reinforcement material, which rubber layer may expand to one orseveral bubbles, which of course result in severe functionaldisturbances and ultimately may break and completely suspend thefunction.

In order to solve these problems and reduce said risks there is providedaccording to the invention a method of forming or designing thesemembrane sections, which, when the membrane is applied, do not contactsupport surfaces and do not relocate or are deformed, when applied,respectively, at least partially with a manufacturing form or shape,which deviates from the shape of said sections, when they are applied.

The first embodiment according to the invention is shown in FIGS. 2 and3, FIG. 3 outwardly substantially corresponding to FIG. 1. However, whenstudying the enlarged part of FIG. 3, it is obvious, that thereinforcement layer within the area with the curve 14 mainly is disposedclose below the convex side. This means, that also maximally calculatedpressure drops are not able to press the thick rubber layer on thepressure side of the membrane through the reinforcement layer intoleeside 20 of the membrane. This has been done by manufacturing themembrane in the position shown in FIG. 2 with its curve with the convexside facing the pressure side. The manufacture is done in a way, whichcorresponds to that way, used for the design according to FIG. 1, apositional change for the lower-dies and the upper-dies however havingbeen carried out and the straight part facing downwards rather thanupwards. When a membrane has been cured in its position according toFIG. 2, curve 14 is turned downwards and straight part 15 upwards, theform to be applied, shown in FIG. 3, being obtained, which is retained,since this membrane form is self-stabilizing, which i.a. the morecompact and consequently more elastic bead 16 contributes to.

However, due to the turning inside out of the membrane according to theinvention it has a certain inherent elasticity, which tends to extendthe curve radially outwards. This ought to in certain cases be takeninto consideration and be compensated for, which is done by choosing acurve with a smaller bending radius in the manufacturing phase (see theenlargement part of FIG. 2). Then during the turning inside out into theapplication position an expansion independently takes place to thedesired dimensions (see the enlargement part of FIG. 3).

Compared to the conventional form according to FIG. 1, which is notprestressed, the form according to FIG. 3 may result in a smalldisplacement of the shoulder area of the curve from the outer side ofthe annular portion and the flange, since this shoulder area is bentalmost 180° compared to the manufactured form. However, this probably isof no practical significance. in case some importance would be attachedto it, a possible counter-measure would be to make the membrane somewhatthinner within the area with bend 11.

A projection 10 may be dispensed with completely, when selecting thedesign according to FIG. 2 and 3, since in the manufacture positionaccording to FIG. 2 there is no requirement, that a form part bepositioned below the curve.

Finally, it is to be noted, that the radial inside portion of the beadin the manufacture phase will be its radial outside portion in theapplication position. Consequently, a desired or existing bend and edgerespectively is mounted during the manufacture on the opposite side inthe radial direction in relation to the desired position during themounting.

However, it is not necessary to manufacture an “upside-down” curve andthen remake it to such a curve turned the right way. The designsaccording to FIGS. 4-7 show ways to, during the manufacture, extend themembrane section for the contemplated curve mainly with a straightdivergence downwards, which can be described in a simple way, referencebeing made to FIGS. 10-12. Support plate 2 is there positioned in or ona lower mold tool half 21, which by means of the inner side of anupwardly projecting pointed ring 22 closely abuts the outer side ofaxial flange 5. The latter may adjacent ring portion 3 be somewhatextended in a step-like manner in a radial direction, whereas in thesame plane as the ring portion a bend 23 projects further outwards inthe radial direction and softly changes into bearing surface 44. Betweenbend 23 and joint 24 of ring 22 a small cut 25 is made, which during thecure will be filled with rubber material. The outer side of ring 22diverges somewhat and mainly straight downwards but with a small bevelor bend 26 adjacent the point and a similar bevel or the like 27adjacent the suitably radially outwardly extended stop face 28 of lowermold half 21, which stop face in its inner part has an annular void 29,against which bevel or the like 27 abuts and which is designed to formone side of bead 16. Thus, the two bevels or the like 26 and 27 areturned radially inwards with a small angle from the preferably straightintermediate portion 30 between them.

Upper mold tool half 31 is mainly form-complementary in relation to thelower one, abuts with a stop face 32 stop face 28, has a void 33, whichis complementary in relation to the bead form and is, similar to thelower mold half provided with a bevel or the like 34 at a distance,equal to the membrane thickness, facing bevel or the like 27. However,an upper bevel or the like preferably is missing and instead straightportion 35, mounted on straight intermediate portion 30 of the mold toolhalf at a distance equal to the thickness of the membrane, continues allthe way up to upper surface 36, located above bearing surface 4. Thelatter and straight portion 35 are connected to each other in the formof a soft bend and thus also provide space for a certain membraneenlargement 37 within the area with bevel or the like 26. For the restthe mold halves are designed in a conventional way to obtain the desiredmembrane shape.

According to FIG. 10 a support plate 2 has been disposed on the lowermold tool half and also an e.g. plane and cut membrane blank 39,provided with a central hole 38 and comprising two rubber layers 40 and41, possibly connected to each other and preferably having a uniformthickness, and between the rubber layers a reinforcement layer 19, e.g.made of a somewhat thinner fabric

According to FIG. 11 the upper mold tool half has been lowered half-wayonto the lower mold tool half, the deformation of the membrane blankbeing started.

According to FIG. 12 the two mold tool halves have been completelybrought together and in this position a curing and corresponding shapingof the membrane takes place. Thanks to the described and shown designalready during the final phase of the transition from the positionaccording to FIG. 11 to the position according to FIG. 12 a stretchingof the membrane blank from the bearing surface to the bead takes place,since the mold tool halves between these two areas do not move straighttowards each other, but the upper mold tool half slides past the lowerone during their approach to each other. Finally, the two lower bevelsor the like 27 and 34 and the adjoining void edges keep the membraneblank within this area between them in the shape of a nip, which pullsalong and stretches the membrane somewhat against the action of lowerrubber layer 41. However, this elasticity is suspended during the cureand becomes a softening, which allows the somewhat tight reinforcementlayer to penetrate somewhat into the lower rubber layer, the softenedmaterial of which penetrates somewhat through the reinforcement materialand is joined with upper rubber layer 49, which is shown in FIG. 12. Inthis position the rubber cures and the membrane becomes rigid, whichthus has obtained an eccentrically disposed reinforcement layer. The twoin the same direction gently angled bevels or the like 26 and 27 andstraight intermediate portion 30 between the two bevels, which isrelatively long in its axial direction, are responsible together withsaid nip and also the somewhat larger distance between the mold halveswithin the are of enlargement 37 for an adequate, i.e. gentle anduniform stretching force, applied to the reinforcement material, whichin its turn can react in a corresponding way, i.e. with a uniformdisplacement into the lower rubber layer, a satisfactory and above alluniform working function for the membrane being secured.

The last-mentioned uniformity is illustrated by the obtained operatingor mounting position according to FIG. 5, where the uniform extension ofthe reinforcement material throughout the entire curve is clearlyvisible. Only within the area of the curve shoulder is there a risk,that the reinforcement material will completely penetrate the lowerrubber layer. However, enlargement 37 is able to protect and stabilizeand prevent this from causing any functional disturbances or a prematurematerial fatigue.

The embodiment according to FIGS. 6 and 7 corresponds to a high degreeto the embodiment described above, but enlargement 37 surrounds bend 23more completely than in the other embodiments and consequentlyconstitutes a larger membrane support within the shoulder area of thecurve. This embodiment is obtained by means of the form shown in FIGS.10-12.

Finally, the embodiment according to FIGS. 8 and 9 shows a method ofobtaining a centrally placed reinforcement material by giving only aportion of the curve, i.e. its outer part, located adjacent the bead, ashape with a more pronounced, differing manufacturing form in comparisonto the application form. It is shown, that the part of the curve,located close to the bearing surface during the manufacturing in aweakened form corresponds to the desired application form, whereas theouter part is turned in the opposite direction compared to theapplication form. These two manufacturing curves, turned in mutuallyopposite directions are able to prevent, that one-sided tensile forceswill influence the reinforcement material, which instead will remaincentrically disposed, which is clearly indicated in FIG. 9.

The present invention is not limited to the embodiments described aboveand shown in the drawings but can be modified and supplemented in anarbitrary fashion within the scope of the inventive idea and theenclosed claims. Thus, any parts may be changed to any design and therereplace and supplement the corresponding parts. Also, no support plateor other support elements are necessary. Thus, a membrane according tothe invention can be manufactured individually or be manufacturedtogether with arbitrary components. Beads and curves are not necessary.Also, in an arbitrary way designed, e.g. in their entirety more or lessplane, membranes are included in the invention. In its simplest form amembrane according to the invention can comprise only one rubber layerand one reinforcement layer. Thanks to the fact, that the latter isfastened against the rubber layer during the cure, it is able topartially penetrate the rubber layer and bring about the characteristicsof the invention.

1-12. (canceled)
 13. A method of manufacturing a membrane (1) by curingone or several membrane blanks (39), which include at least one rubberlayer (40, 41) and at least one permeable reinforcement layer (19), madeof a fabric and placed adjacent the rubber layer and between two orseveral rubber layers, wherein in order to counteract and preventrespectively undesirable displacements of the reinforcement layer (19)certain membrane sections (14), which in an application position do notcontact support surfaces and are displaced or deformed, are manufacturedwith a form or shape, which deviates from the application form, and inthat these membrane sections, by turning them inside out, are givendesirable forms in the mounting and application positions, respectively.14. The method according to claim 13, further comprising the step ofexposing the reinforcement layer and layers (19) respectively to astretching across the rubber layer extension during the cure in orderto, within the membrane section (14), bring about a displacement of thereinforcement layer (19) across a portion of at least one of the rubberlayers (40, 41) and consequently a position during the cure, whichdeviates from the building up of the blank.
 15. The method according toclaim 13, further comprising the step of manufacturing a membrane (1)having a ring section (14), which is convex in the mounting orapplication position, with this section having a concave form and with arubber layer displaced (18) through the reinforcement layer (19) to theconvex manufacturing side, the membrane subsequently being turned insideout to the convex form with the rubber layer displacement to the concaveside.
 16. The method according to claim 13, further comprising the stepof manufacturing in a membrane having a ring section (14), which isconcave towards the pressure side (17) in the application position, thisring section is manufactured on an upper-die part (21), designed mainlyas a converging truncated cone, which is brought to cooperate with asubstantially correspondingly designed lower-die part (31).
 17. Themethod according to claim 16, further comprising the step of providingthe envelope surface of the truncated cone, at one of the base and thetop, with a bevel (26 and 27 respectively) in order to in thereinforcement layer (19) create a tension, directed towards the straightintermediate portion (30), positioned there between, as well as apartial penetration through an underlying rubber layer (41) during thecure.
 18. The method according to claim 17, further comprising the stepof designing the lower-die part (31) to follow the form within the areaof at least one bevel (26 and 27 respectively) and/or to have anenlargement (37) and a thinning respectively.
 19. The method accordingto claim 13, further comprising the step of manufacturing, in order toobtain a reinforcement position which is mainly unchanged in relation tothe blank building up, a membrane ring portion, which is concave in themounting or application position, partly in a concave and partly in aconvex form, preferably with an inner part in a concave and with anouter part in a convex form, and that in the latter part in the mountingand the application position respectively is brought to occupy a concaveform.
 20. The membrane (1), manufactured according to the methodaccording to claim 13, which membrane is made of one or several blanks(39) by curing them and which comprises at least one rubber layer (40,41) and at least one permeable reinforcement layer (19), positionedadjacent the latter rubber layer and between several rubber layersrespectively, and manufactured (19) of e.g. a fabric, wherein in orderto counteract and prevent respectively undesirable displacements of thereinforcement layer (19) certain membrane sections (14), i.e. sectionswhich in the application position do not come in contact with supportsurfaces and change location or are deformed respectively, aremanufactured with a form, which deviates from the application form andshape, and are designed to, in the mounting and the application positionrespectively, be brought to, through a turning inside out, assumedesirable forms or shapes.
 21. The membrane according to claim 20,wherein the reinforcement layer and the reinforcement layersrespectively (19) in the membrane section (14) are at least one ofposition-adjusted and tension-adjusted in relation to the blank buildingup through a displacement across a portion of at least one of the rubberlayers (40, 41), since they during the cure have been exposed tostretching.
 22. The member according to claim 20, wherein the membrane(1) has a ring section (14), which in the mounting or applicationposition is concave in relation to the leeside (20), and is manufacturedwith this section having a concave form and with a rubber layerdisplacement (18) through the reinforcement layer (19) into the convexmanufacturing side, and in that the manufactured ring section (14)having a concave form is turned inside out to a convex form with therubber layer displaced to the concave side.
 23. The membrane accordingto claim 20, wherein in order to obtain a reinforcement position, mainlyunchanged in relation to the blank building up, a membrane ring part,which is concave in the mounting or the application position, ismanufactured partly in a concave and partly in a convex form, preferablywith an inner concave and an outer convex part, and in that the latterpart, in the mounting and in the application position, is turned insideout in order to assume a concave form.
 24. The mold or die tool,designed to carry out the method according to claim 13, wherein whichmold tool has an upper-die (21) and a lower-die (31) and is designed toreceive e.g. plane membrane blanks in the form of at least one rubberlayer (40,41) and at least one reinforcement layer, and to soften therubber layer through curing and form the membrane, in order tocounteract and prevent respectively undesirable displacements of thereinforcement layer (19), certain mold tool sections, designed forcertain membrane sections (14), i.e. sections, which in the mounting orapplication position of the membrane have no contact with supportsurfaces and change positions or are deformed respectively, are designedwith a form, which deviates from the mounting or application form of themembrane and which is designed to obtain the membrane in its mountingand application position by turning it inside out.